1. Field of the Invention
The present invention relates generally to lift systems for vehicles and more particularly, to a self-contained lift system for use on a vehicle incorporating hydraulic jacking units operable from a central controller located inside the vehicle.
2. Description of the Prior Art.
Self-contained vehicle lift systems featuring hydraulic jacks are known in the prior art; however, these typically are large, complicated units, expensive to install and operate, and prone to malfunction. For example, U.S. Pat. No. 4,235,542 discloses a hydraulic lift unit adapted to be mounted on a vehicle wherein a hydraulic motor, hydraulic pump and valve assembly are mounted inside the jack's cylinder. This unit because of its relatively large bulk must include additional means for rotating the jack assembly about a pivot support to an unused position.
Similarly, U.S. Pat. No. 4,635,904 discloses a self-contained vehicle lift system wherein the jacking units are activated by a complex motor-driven gear arrangement. Here again, the relatively large jacking unit is pivotally mounted on the vehicle frame and includes means for rotating the unit from a vertical to a horizontal position.
Other lifting devices have been proposed for stowage aboard a vehicle. For example, in U.S. Pat. No. 4,542,882, an inflatable bag is disclosed having a fitting connected to the exhaust pipe of a vehicle. It is apparent, however, that this device may be used only with the vehicle engine running, a situation which can be dangerous to the vehicle operator.
Finally, portable jacking units are known for use with vehicles, which are capable of being stowed on the vehicle. U.S. Pat. Nos. 4,549,722 and 4,690,378 disclose examples of the latter type. It is apparent, however, that the operator must get out of the vehicle to operate such units, thereby presenting an inconvenience and possible danger from passing vehicles.